The invention relates to a device for influencing the deployment of a gas bag of an airbag module.
The deployment of the gas bag must be controlled, for example to improve its out of position (OOP) behavior, especially in cases with additional means in which the gas flows out in such a way that the gas bag is not deployed uniformly, or not symmetrically, in the direction of the occupant, or is deflected unintentionally in a certain direction, and more especially in cases in which the outflow openings on the generator are not provided in the middle of the module but are provided asymmetrically with respect to the middle of the module. An example of this is that of most hybrid gas generators for passenger airbag modules. Various solutions for influencing the deployment of a gas bag of an airbag module have become known.
For instance, DE 44 42 202 A1 discloses a passenger airbag module which, for influencing the gas flowing into the gas bag, is equipped with different diffusers, which have greater outflow openings in the direction of the desired main direction of deployment of the gas bag.
DE-A-2 030 863 discloses the provision of tearing seams for influencing the deployment of the gas bag. In this case, the gas bag can, in a first phase, be deployed up to a size which the intact tearing seams allow. Increasing internal pressure in the subsequent second phase causes the tearing seams to tear, and the gas bag can then be deployed up to its full size.
DE 195 06 886 and EP-A-0 593 010 A1 disclose airbag modules in which retaining straps are provided for the directed deployment of the gas bag. These extend from the gas generator to different locations of the gas bag, without influencing the flow of the gases leaving the gas generator or the diffuser. The retaining straps influence the deployment of the gas bag only on the basis of their different lengths and their fastening locations on the gas bag. It is also the case with these airbag modules provided with retaining straps that the flow of the gases is influenced by means of the diffusers.
The means previously provided for influencing the expansion of the gas bag during its deployment require considerable additional expenditure.
Finally, U.S. Pat. No. 5,464,250 discloses a gas bag in which two retaining straps are provided in the region of the gas generator, extend in their width through virtually the entire gas bag and, together with the wall of the gas bag, form a channel for the gases leaving the gas generator. This retaining strap arrangement is only appropriate, however, for gas bags which are flat after deployment, as is the case with gas bags for side airbags, so that the retaining straps are short.
The invention is based on the object of reducing the expenditure for influencing the expansion of a gas bag independently of the form of the gas bag during its deployment.
In a device for influencing the expansion of a deploying gas bag of an airbag module, the gas bag and/or at least one retaining strap in the region of the outflow openings of a gas generator or diffuser form(s) together with said openings a channel with outflow openings for influencing the gas flowing out after the gas generator is ignited.
This solution is particularly advantageous whenever at least one retaining strap is provided in any case. In this solution, in addition to its customary function, the retaining strap undertakes the influencing of the flow in a predetermined direction or in a plurality of predetermined directions. The solution may be used in addition to a diffuser or as a substitute for a diffuser. By means of this solution, the stress values for the OOP position of an occupant can be reduced. In addition, the solution can always be used advantageously if the deployment or expansion direction of the gas bag has to be influenced.
In a first embodiment, using a tubular gas generator, two retaining straps are provided, extending in their width over a predetermined portion of the length of the tubular gas generator, a first retaining strap extending from one side of the tubular gas generator as far as the location of the gas bag to be influenced in its expansion by the retaining strap, while the second retaining strap extends from the opposite side of the tubular gas generator and is connected to the first retaining strap above the outflow openings of the tubular gas generator or of the diffuser. In this embodiment, between the gas generator and the two retaining straps there is consequently formed a channel into which the gases of the gas generator flow and are deflected there.
In a second embodiment, only one retaining strap is provided, wrapping around the gas generator with one end. This end is then connected to the retaining strap above the outflow openings of the gas generator or the diffuser. In this way, a channel is consequently formed between two portions of the retaining strap and the gas generator.
It is expedient that the second retaining strap or the wrapping-around end of the single retaining strap is connected over the entire retaining strap width to the first retaining strap or to the retaining strap itself or to the gas bag. In this case, a channel which is closed over its entire length and from which the gas can leave only at the end faces is produced. It is also possible, however, to provide at the connecting location an interrupted connection or individual punctiform connections, so that part of the gas can also leave the channel at the sides.
A channel may also be formed without retaining straps, by opposite sides of the gas bag being connected to each other over the gas generator or diffuser. The connection does not take place over the entire width of the gas bag, so that openings through which the gas leaving the gas generator can flow into the gas bag remain free at the ends of the seam.
The connection may take place, for example, by sewing, welding, adhesive attachment or by means of a touch-and-close fastener, it being possible for a single seam or multiple seam to be provided.
The course followed by the connection location may be chosen according to the desired outlet direction of the gases. The connecting location may therefore follow a linear or two-dimensional course.
A further embodiment provides that the channel has a differing cross-sectional size over its length. This makes it possible to influence the velocity of the gas, so that a diffuser action is also achieved by means of this retaining strap device.
In one embodiment, the channel has an enlarging cross section in a desired preferable direction of expansion of the gas bag.
In a further embodiment, it is provided that the retaining strap and/or the retaining straps or one of the retaining straps have clearances in the region in which they form the channel. In this case, the gas can, as in an embodiment with an interrupted seam, also leave the channel at the sides. In this embodiment, the diffuser action is further intensified.
In a further embodiment, it is provided that the longitudinal edges of the retaining strap or of the two retaining straps, extending from the connecting location of the end of the retaining strap with itself or extending from the connecting location of the second retaining strap with the first retaining strap are connected to each other over a predetermined length in the direction of the gas generator. This produces in addition to the channel a shaft in which part of the gas flowing out from the gas generator is initially intercepted. This fraction of the gas then flows out of the channel with a delay. This embodiment consequently allows still further influencing of the gases flowing out. This embodiment may also be modified to the extent that the connection running in the direction of the gas generator is interrupted and begins at a distance from the connection of the two retaining straps. This produces additional outflow openings for the gas.
Since the retaining straps are additionally subjected to the hot gas in the region of the gas generator, it is expedient for the retaining straps to have different thicknesses or, if one retaining strap is used, for the end of the retaining strap wrapping around the gas generator to be strengthened.
As a departure from the embodiment represented, when using two retaining straps the two part retaining straps may vary in their length and form and do not have to be made identical or similar.
In one embodiment it is provided that the connecting location of the end of the retaining strap with itself or of the second retaining strap with the first retaining strap is designed as a tearing seam. In this case, the connection of the retaining strap end or of the two retaining straps is initially used for diverting the gas in the desired direction. Subsequently, the connection tears open partially or completely.
The deployment characteristics of the gas bag may also be influenced by the combinations of connections or part connections of the retaining straps arranged vertically, horizontally, obliquely or in a curved manner.